Commit 24b2ec21 authored by Alexey Dobriyan's avatar Alexey Dobriyan Committed by Linus Torvalds
Browse files

proc: check permissions earlier for /proc/*/wchan 

get_wchan() accesses stack page before permissions are checked, let's
not play this game.

Link: http://lkml.kernel.org/r/20180217071923.GA16074@avx2


Signed-off-by: default avatarAlexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent d0f02231

fs/proc/base.c

+8 −5
Original line number Diff line number Diff line
@@ -388,14 +388,17 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns, 
	unsigned long wchan;

	char symname[KSYM_NAME_LEN];



	wchan = get_wchan(task);

	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))

		goto print0;



	if (wchan && ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)

			&& !lookup_symbol_name(wchan, symname))

	wchan = get_wchan(task);

	if (wchan && !lookup_symbol_name(wchan, symname)) {

		seq_printf(m, "%s", symname);

	else

		seq_putc(m, '0');

		return 0;

	}



print0:

	seq_putc(m, '0');

	return 0;

}

#endif /* CONFIG_KALLSYMS */